= Solution
{c}
\b[TODO (source gap):] Figure 1(a), including its internal connections and <four-momentum> labels, is absent from the recoverable source. The local PDF renderer reports missing image objects, and the matching official PDF's figure could not be retrieved for visual inspection. Therefore the individual <Feynman diagram> called (a) cannot be assigned an integrand and its separate independence of $\xi$ cannot be verified from the available diagram. A guessed replacement drawing would not resolve this gap.
An independent determination of the complete <ultraviolet pole>, given in part (iv), remains possible from the <scalar QED Ward identity>. Together with the textually supplied integral in part (iv), it fixes the sum of the contributions outside that integral to $3ie^3C_\epsilon k^\mu$ in the stated <scalar electrodynamics three-point vertex> convention. That sum alone does not identify the contents of panel (a).
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